1. Technical Field
The embodiments described herein relate to an orthotic system molded in situ on the head of an associated patient, to the fabrication or set up methods of the orthotic system on the patient's head, and to the use of a cranial orthotic system for the modification of cranial shape for treatment of, for example, plagiocephaly, post-operative cranial molding, and the like.
2. Background Art
Plagiocephaly is characterized by an abnormal cranial shape which can occur in response to external pressure, or due to premature fusion of cranial sutures in infancy. Infants who develop plagiocephaly can have additional distortion of other craniofacial structures in response to external molding pressure, frequently involving the orbit, face, and cranial base. This pressure can take the form of intrauterine contact with the maternal pelvis, prolonged pressure in the birth canal, or chronic pressure from sleeping in one position. Additional risk factors for developing positional or deformational plagiocephaly include multiple births, congenital torticollis or neck tightness, developmental delay or neurologic impairment which precludes normal infant movement, uterine abnormalities, and genetic influences.
The incidence of positional plagiocephaly has been rising due to increased numbers of infants sleeping in the supine position. In 1992, the American Academy of Pediatrics began the “Back to Sleep” campaign, maintaining that all infants should sleep in the supine position to decrease the incidence of crib death or SIDS (Sudden Infant Death Syndrome) which has been linked to prone or side sleeping. This has resulted in an epidemic of plagiocephaly which affects up to 1 in 8 live births in the U.S., according to some estimates. Despite the increased incidence of plagiocephaly, the campaign has resulted in a decrease in SIDS by more than 40%, and will likely continue into the foreseeable future. Therefore, measures to avoid plagiocephaly or treat it after it has developed have been devised.
Additionally, premature fusion of one or more of the cranial sutures can lead to similar alterations in cranial shape, called craniosynostosis. Conventional surgical therapy involves removing the cranial bones, physically remodeling them, and rigidly fixing them in place in their new form with plates, screws, or other mechanical fastening methods. A newer approach has evolved to permit endoscopic or minimally invasive release of the fused or synostotic cranial sutures. This method relies upon subsequent expansion of the growing brain to remodel the cranium, or the use of springs or appliances which cause expansion of the cranial vault, creating a role the use of molding helmets or orthotics for directing postoperative cranial growth.
A number of methods have been described to alter cranial shape, with historical examples dating back to the early early Olmec culture (1400 BC-400 AD) in what is today modern Mexico. These Mesoamerican inhabitants used external compression to alter cranial form for aesthetic purposes. In the modern era, external compression techniques have been used to treat plagiocephaly. The growing brain provides the impetus for early cranial growth, leading to expansion of the cranial vault across the cranial sutures, which are essentially biological expansion joints. Similarly, these forces are harnessed to permit remodeling or molding of the cranium.
There are several categories of devices or techniques known in the art which have been used for the treatment of plagiocephaly. These include simple positioning of the infant to minimize deforming forces, the use of wedges, pillows, or mattresses, and primitive helmet or band type orthoses.
Current recommendations for initial treatment for early positional plagiocephaly include positioning the infant so that there is no pressure on the flattened area of the cranium, relying upon periodic checks during the night to ensure compliance. This method is hampered by poor parental acceptance due to the need for frequently awakening during the night to check on the infant. Further, the infants often prefer to lie upon the flattened area, exacerbating the problem.
Other techniques to improve plagiocephaly can include the use of wedges or pillows to alter pressure on the infant's head. The success of these positioners is also hampered by the infant's activity level. Once they are capable of rolling over, they can move out of the desired sleep position.
Other strategies for redirecting pressure on the head include devices which tip or bolster the sleeping surface. These devices are also limited in utility by the mobility of the infant, who can move out of ideal position, thus rendering the mattress or pad device ineffective. Further, the force of gravity can only be transmitted to the cranium by the dependent portion of the head, limiting the overall distribution of the remodeling forces.
Another category of devices to treat plagiocephaly include orthotics and helmets that fall generally into the categories of active or passive cranial molding devices. The force of the growing brain can be directed to specific areas of the cranium by constraining growth in a portion of the head, permitting the growing brain to exert expansile forces in areas not covered by the orthotic. The first class of devices are designed to actively apply pressure to some or most of the cranial surface. Although these devices are marginally effective in modifying head shape, there are additional concerns that active molding appliances can result in more frequent soft tissue injury, hair loss, and potential discomfort to the patient, rendering this approach less desirable to the practitioner. Further, there are theoretical concerns that these devices can increase intracranial pressure, resulting in potential local injury to the brain, and potential developmental delay. The other class of cranial molding devices are roughly adapted to approximate the shape of the patient's head and, accordingly, do not actively exert pressure. There are some data which suggest these devices designed to function passively have less risk of elevating intracranial pressure, with less potential for affecting brain development. Passive cranial molding orthoses involve helmet or band-type devices which constrain head growth in areas of more normal shape, permitting further growth in areas in which the helmet either has less pressure, or does not make contact. These devices rely upon an intimate contact with portions of the more normally shaped cranium, constraining growth in these areas, and directing the expansile forces of the brain to the areas of the orthosis in which there is no contact with the cranium. These methods are most effective in modifying craniofacial shape during early infancy when craniofacial growth is rapid.
Within the category of helmet orthoses, methods of active cranial molding utilize pneumatic bladders to mold the head. However, these devices rely an initial plaster model of the infant's skull fabricated, followed by construction of a custom helmet with a plurality of pneumatic bladders to apply pressure to various parts of the head, thereby increasing molding forces and directing growth towards the portion of the helmet where there is no contact. This method has the drawback of imprecise direction of molding forces due to the limited number of bladders which can be included, difficulty in ensuring even application of pressure along the bladder margins, and the general drawback of the use of active molding forces, which may cause unforeseen problems to the growing brain.
Practitioners skilled in the art have recognized that customized cranial orthoses which are specially designed for each individual patient are most effective in restoring normal cranial form to the affected infant. These helmets have been historically fabricated by taking a plaster cast of the patient's head, using the plaster cast as a negative mold to create a positive mannequin form which is a fair representation of a copy of the patient's head shape, then molding a custom orthotic upon this mannequin head. Alternately, this process can be carried out with laser scanning to create a virtual model of the patient's head, followed by the creation of a stereolithographic or CAD milled model or mannequin of the patient's head, followed by custom molding of the orthotic device on the mannequin. These methods are somewhat effective, but are cumbersome, time-consuming, and expensive. Additionally, they require significant expertise in both computer image manipulation, and in fabrication of orthotic devices in order to achieve an acceptable result.
In practice, the use of a positive model upon which to create the molding helmet/orthosis, and the use of an expert system software utilizing an anthropomorphic database to generate a positive model of the desired head shape, requires a skilled orthotist to create the appropriate computer file modifications to design the appliance, the use of stereolithographic or CAD milling methods for creation of the intermediate mannequin, and multiple visits for the patients due to time constraints involved in the manufacturing process. Importantly to the patient's treatment regime, the creation of a positive model from either a physical cast or a virtual three-dimensional image requires at least two patient visits, including a first visit to acquire the actual or virtual mold of the patient's head, an interval to permit time to create the model and fabricate the orthotic upon the mannequin head, followed by a secondary visit to check the fit and form on the head of the patient. This typically takes weeks to carry out, resulting in significant expense and inconvenience to the patient's family and results in delay of treatment. More importantly, this indirect casting method creates inaccuracies in helmet fit related to the loss of detail which begins with the initial casting or laser scan, then in the generational conversion of scan data to CAD data, subsequent manipulation of those data, the creation of the negative molds, and finally with the secondary molding upon the mannequin head.
Most devices of this class use a layer of foam as the substrate to transfer pressure to the patient's head. In the majority of these devices, a solid sheet of the foam is heated and molded upon the positive form, followed by vacuum thermoforming of the polymer shell material upon the foam liner. This method uses manufacturing techniques which are unsuitable to application in situ on the patient's head owing in part to the specialized equipment and to the high temperatures needed for material forming and handling.